What I have noticed from visits to City Hall is that the art that's there is quite accessible is a tile mural that you can not only see without going through a checkpoint, but is even so ready to hand that you can touch it.

A proposal was put forth to not spend the money on art and to renovate some bathrooms in the building instead. This left a missed opportunity to instead ready-made art as part of that installation. (photo: wikimedia commons, from the original photo by Alfred Stieglitz).